Southernmost occurrence of <i>Purgatorius</i> sheds light on the biogeographic history and diversification of the earliest primate relatives
Bibliographic record
Abstract
Fossils of the earliest known euarchontan mammals, purgatoriid plesiadapiforms, first appear during the aftermath of the Cretaceous/Paleogene mass extinction. The oldest and most basally branching plesiadapiform, Purgatorius, has been documented in Montana and Saskatchewan during the earliest Paleocene Puercan North American Land Mammal Age, but no plesiadapiforms have been recovered from southern basins of the Western Interior until later in the Paleocene. This temporal and geographic gap has made the early biogeographic history and diversification patterns of plesiadapiforms unclear. Here we report Purgatorius fossils recovered from extensive screen-washing of sediments from the Corral Bluffs study area, Denver Basin, Colorado, which represent the first Puercan occurrence of a plesiadapiform south of Montana. Isolated teeth of Purgatorius described here exhibit a unique combination of features, and may represent a new, early diverging species. This discovery bridges the temporal and geographic gap among the earliest plesiadapiforms and suggests a northern origin followed by a southerly diversification in the earliest Paleocene. The presumed absence of Puercan plesiadapiforms in southern regions of the Western Interior of North America was at least in part due to sampling biases. Additional screen-washing efforts in these regions will further clarify biogeographic patterns of plesiadapiforms and other small-bodied earliest Paleocene mammals.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".